Efficient removal and recovery of uranium from industrial radioactive wastewaters using functionalized activated carbon powder derived from zirconium carbide process waste.

Abstract

Development of efficient sorbents for selective removing and recovery of uranium from radioactive wastewaters is highly important in nuclear fuel industries from the standpoint of resource sustainability and environmental safety issues. In this study, carbon powder waste was modified by various chemical activating agents under atmosphere of nitrogen gas at 725 °C to prepare an efficient sorbent for removal and recovery of uranium ions from radioactive wastewaters of nuclear fuel conversion facility. Activation of the carbon powder with KOH, among different activators, provided maximum porosity and surface area. The activated samples were modified by reacting with ammonium persulfate in sulfuric acid solution to generate surface functional groups. The synthetized sorbents were characterized with FT-IR, XRD, BET, and SEM-EDS techniques. The effects of solution pH, contact time, initial uranium concentration, and temperature on the sorption capacity of the sorbent with respect to U(VI) from wastewater were investigated by batch method, followed by optimizing the effect of influential parameters by experimental design using central composite design. The sorption of UO22+ ions on the sorbents follows the Langmuir isotherm and pseudo-second-order kinetic models. Maximum sorption capacity for U(VI) was 192.31 mg g-1 of the modified sorbent at 35 °C. Thermodynamic data showed that sorption of U(VI) on the sorbent was through endothermic and spontaneous processes. The sorption studies on radioactive effluents of the nuclear industry demonstrated that the modified sorbent had a favorable selectivity for uranium removal in the presence of several other metal ions.